Cactus (Cactaceae)

The cactus is synonymous with loneliness and aloofness. Some 50 million years ago, an ancient thorn bush warded off herbivores with its sharp spines and from that ancestor we get the modern cactus, of which there are over 2,000 species. These plants are as tough as plants get -- some can grow as tall as trees and many of them survive in the driest deserts on the planet. One particularly masculine species is the "old man cactus" (cephalocereus senilis) whose white hairs make it look, unsurprisingly, like a haggard old man.